Measuring devices are known. For example, electrochemical sensors, formed in a so-called finger type of construction, are installed in motor vehicles for determining the oxygen content in the exhaust gases of internal combustion engines. These measuring devices possess one sensor element which is arranged directly at a measuring point and which is tightly secured in a housing.
The sensor element, as is known, has a solid electrolyte arranged between two electrodes. According to the makeup of the sensor element, an additional heating element is provided. To evaluate the sensor signals detected by the sensor element, or to supply the sensor element with the necessary heating voltage, provision is made for electrical connecting lines, which connect the sensor element to a corresponding circuit arrangement.
Since the sensor element, for example in measuring the oxygen content in exhaust gases, is arranged in an area which is acted upon by a relatively high temperature and in which an increased danger of contamination exists, it is known to shield the electrical connecting lines at least in the vicinity of the measuring device. For this purpose, it is known to run the electrical connecting lines in a protective device designated as a hollow lead. This hollow lead, which is also made of an elastic hose, engages with a shoulder (collar) of the measuring device housing and forms a sealing seat with the latter. In this connection, a form-locking fit obtains between the protective device and the housing. The known sealing seat has the disadvantage that although sufficient protection is afforded against coarse contamination, e.g., from spray water, nevertheless, fine contamination, such as is caused by a mist-like condensation, as occurs precisely in the mounting location of measuring devices in motor vehicles, is not countered by an adequate sealing effectiveness.
The mist-like condensation spreads along the sealing surfaces of the protective device and the housing, which form the sealing seat, and in this way penetrates into the interior of the measuring device.